An Exploratory Study of Cortisol Reactivity and Recovery Among Young Adolescents: Age, Gender, Heterogeneity

The human response to stress and the influence of stress on physical and mental health has long been a topic of great scientific interest. Hormone secretion has been identified as a vital function for organisms to survive and to respond to stressor, and the use of cortisol to understand the stress-response system has increased dramatically over the last decade. While a biopsychosocial model of human behavior has been widely accepted, biological marker of stress-response has been rarely incorporated in social work research. Research has proposed two components of cortisol response following exposure to a stressor. Cortisol reactivity represents increased cortisol secretion observed immediately following a stressor and is an indicator of sensitivity to that stressor. Cortisol recovery indicates the degree to which the immediate response to stressor persists or returns to normal (Linden et al., 1997). However, relatively little research has been conducted on cortisol recovery (Brosschot et al., 2005; Linden et al., 1997). Despite the recent increase of interest in investigating both cortisol reactive and recovery (MacMillan et al., 2009; Powers et al., 2006), the findings are inconsistent. Further, the limitation in the statistical approach in the previous research, which could not estimate cortisol reactivity and recovery simultaneously, contributed to the lack of clear understanding cortisol reactivity and recovery. This study examined cortisol reactivity and recovery following exposure to a laboratory stressor using a piece-wise latent growth curve (PLGC) model. The PLGC model is based on multiphase regression models in which two or more regression slopes are connected. The model estimates cortisol reactivity and recovery as a separate phase of cortisol response. Next, the study examined whether age and sex explained the variability in cortisol reactivity and recovery. Then, the study investigated heterogeneity in the patterns of cortisol response using latent class analysis. Participants were 135 healthy young adolescents participating in a longitudinal study of puberty and psychological development. Three waves of longitudinal data were collected at six-month intervals. In each wave, 5 saliva-cortisol samples were collected prior to and following a modified Trier Social Stressor Test for Children (TSST-C; Kirschbaum et al., 1993). The results suggest that the PLGC model is useful to describe cortisol reactivity and recovery. Older adolescents were more reactive to the stressor suggesting that social cognitive challenges become more salient with age. The sex differences showing higher reactivity in girls at Wave 3, suggest that girls are becoming increasingly sensitive to stressor with advancing age. No significant relationship between reactivity and recovery suggests the independence of two components. Latent class analyses of each wave of data identified three unique subclasses. To some extent, class membership remained stable across waves but there was also a change of membership. Further, the study identified the four subgroups representing different longitudinal patterns of cortisol response. Heterogeneity found in the pattern of cortisol response suggests exciting hypotheses to be tested: whether identified the classes differ in their emotional and behavioral functioning. This research significantly contributes the advancement of theory of human behavior and transdisciplinary social work research on stress-response.